JP3411542B2 - Lighting method and lighting device for high pressure discharge lamp - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a lighting device for a direct current high pressure discharge lamp, and more particularly to a lighting device which can prolong the life of a lamp without impairing good startability.

[0002]

2. Description of the Prior Art A method of lighting a DC-lit high pressure discharge lamp is known for power control, for example from U.S. Pat. No. 4,240,009.

That is, as described in the claim 1. (d), the control is such that a constant current is supplied when the lamp rises and then a constant power is supplied when the lamp is stably lit.

The lamp current immediately after the high-pressure discharge lamp is started is at least 1.2 to 2 times as high as that at the stable time, and it is generally aimed to quickly start up.

However, it takes at least several minutes until the temperature becomes stable, and at each start, the high lamp current immediately after the start promotes the scattering (sputtering) of the tungsten electrode of the cathode. Then, the scattered tungsten adheres to the tube wall and so-called blackening occurs.

Optically, blackening causes attenuation of light quantity,
It also causes the surface temperature of the lamp to rise, resulting in a decrease in the lamp life.

In order to reduce such electrode scattering as much as possible, electrodes having a structure with a coil have been conventionally used. It is said that this structure reduces scattering due to ion bombardment. In addition, the arc spot is quickly formed on the tip of the electrode at the time of starting. That is, the electrode mandrel is protected by the coil.

In the conventional high pressure discharge lamp such as a metal halide lamp of several tens of atmospheric pressure level, the above-mentioned lighting method using the lamp current has no particular problem.

However, recently, ultra-high pressure mercury lamps of 100 atm or more have been actively developed, and in the conventional electrode with a coil, an arc is likely to be formed from the edge of the coil or the like at the initial stage of starting, so that the coil part Another problem arises in that the temperature becomes abnormally high and easily melts.

Even with a slight melting of the electrode, the impure alkaline component contained in the tungsten of the coil appears in the lamp, which causes a chemical reaction with the quartz glass to cause crystallization of the glass and devitrification, resulting in a shortened life. Was there.

In that respect, an electrode of a single mandrel which does not use a coil (there are various shapes such as a cylinder, a shape in which the end of the cylinder is sharpened, a shape in which the end of the cylinder is rounded, and an end of the cylinder (There is a shape in which the portion is sharpened and the tip is rounded, etc.) is advantageous because electrode melting does not easily occur, and it is easy to apply to recent ultra-high pressure mercury lamps because it can potentially achieve a long life.

However, since there is no coil, as described above, the electrode surface of the single mandrel is likely to be scattered by the ion bombardment at the time of starting, so that the blackening at the time of starting the lamp is promoted and the luminous flux maintenance factor is deteriorated. Occurs.

These problems become particularly noticeable in a short arc high pressure discharge lamp having an arc length of 2 mm or less.

This was verified by making a 270 W ultra-high pressure mercury discharge lamp as a prototype and lighting it by a conventional lighting method.

The outer diameter of the bulb is 14.5 mm, the arc length is 1.3 mm, and the cathode is a tungsten mandrel with a diameter of 1.4 mm.
We made a prototype atmospheric pressure lamp and tried lighting it with direct current.

FIG. 2 is a diagram for explaining power control characteristics according to a conventional lighting method, showing a lamp current characteristic and a lamp power characteristic with respect to a lamp voltage. FIG. 4 shows a waveform for explaining the lamp current at the time of starting by the conventional lighting method.

The lamp voltage during stable lighting in the early stage of aging is approximately 55V to 85V, and the lamp voltage rises by approximately 15V at the end of life with aging. Therefore, as shown in Figure 2, at least 55V to about 100V
The area up to has a characteristic of maintaining a constant power of 270W.

The rising period was about 7A. This is about the lamp current (about 5A) required to supply 270W when the minimum voltage during stable lamp lighting is 55V.
1.4 times. Generally, it is often doubled to about 10A.

Particularly in an ultrahigh pressure mercury lamp of 100 atm or more, the arc is squeezed, the temperature of the bright spot of the electrode is high, and the current density of the electrode is also high. That is, the electrode consumption due to thermal evaporation during stable lighting becomes severe, the electrode tip is consumed due to aging, the arc length is apparently lengthened, and the luminous flux maintenance factor decreases.

In order to solve such a problem, the weight of the cathode tungsten electrode is designed to be heavier as the ultrahigh pressure is increased. In this example of the lamp, the electrode weight is about 230 mg,
For example, an equivalent 270W lamp weighs 1.5 times as much as the electrode of a lamp at about 70 atmospheres.

Therefore, in the rising period at the initial stage of starting, 1.2 to 2 times as much current as in normal stability is required in order to properly heat the electrode to quickly bring it into a stable state.

However, under this condition, the lamp is turned on / off.
When the lamp was turned off repeatedly, a blackening phenomenon in the lamp was noticeably found about 50 times. As a result, the luminous flux maintenance factor becomes 70% in about 100 hours, and the decrease is remarkable.

[0023]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a lighting method and a lighting device for a high pressure discharge lamp which can maintain the original long life of the lamp without impairing the starting performance of the lamp.

In particular, a rare gas and mercury are enclosed in the arc tube, the arc length is 2 mm or less and 400 W or less, and the tungsten current of the cathode is supplied with a DC lamp current to a high-pressure discharge lamp composed of a single mandrel. In the method of lighting, it is an object to suppress the scattering of the current substance of the cathode at the time of starting to suppress the life reduction due to the blackening of the lamp and to prevent the startability from being impaired and to obtain a fast start-up of the lamp.

[0025]

According to a first aspect of the present invention, there is provided a method for lighting a high pressure discharge lamp, wherein a rare gas and mercury are enclosed in an arc tube, an arc length is 2 mm or less and 400 W or less, and a cathode tungsten electrode is used. A method of lighting a high-pressure discharge lamp composed of a single mandrel with a direct current lamp current, in which a starting initial current is supplied for a predetermined period during the initial period of lamp startup, and then a constant current is maintained during the lamp startup period. controlled, subsequently, lamp during stable lighting is controlled by Ryakujo power, the current value of the substantially constant current of the lamp rise period current value that can supply a constant power in a stable lighting mode prescribed minimum voltage of the lamp
Or more, the current value of the initial start-up current is below the current value of the lamp rising period, sputtering when energized
It is characterized in that the current value is within a range in which the engine does not occur and can be started .

According to this, during a period in which the position of the arc spot is unstable immediately after starting, the current is appropriately set to prevent the electrode from spattering, and the load on the electrode can be reduced. Therefore, the original long life of the lamp can be maintained.

Then, after the arc spot moves to the tip of the electrode and stands still, the current can be set appropriately high to accelerate the rise time of the lamp, so that the startability is not impaired.

A high pressure discharge lamp lighting method according to a second aspect of the present invention is the lighting method according to the first aspect, characterized in that the fixed period at the beginning of the lamp is 10 seconds or less.

This is to focus on the fact that the position of the arc spot immediately after starting is unstable for 10 seconds or less, and changes the current value after the arc spot moves to the tip of the electrode and stands still.

A high pressure discharge lamp lighting device according to a third aspect of the present invention comprises a DC power supply (1) for supplying a DC current for lighting the high pressure discharge lamp, and a current detector for detecting the lamp current as a detection voltage.
The output circuit (6) and the voltage that detects the lamp voltage as the detection voltage.
A pressure detecting circuit (7), is connected to the direct current power source (1), the run
A down converter (2) that controls the power of the high-pressure discharge lamp (5) from the current detection voltage and the lamp voltage detection voltage ,
An inverting amplifier (16) for inverting and amplifying the detection voltage detected by the voltage detection circuit (7), and the detection voltage detected by the current detection circuit (6) and the output of the inverting amplifier (16) are added. Down based on the adder circuit (15) and the output of the adder circuit (15)
The converter (2) controls the pulse width and the high-voltage discharge
Pulse width modulation circuit (9) for controlling the power of the lamp (5 )
And the lamp connected to the output of the inverting amplifier (16)
The current value during the rising period is
The current value must be less than the current value that can supply constant power at the specified minimum voltage.
Voltage limiter circuit as defined in so that the (17), a lamp start
Immediately after that, the voltage limiter circuit (17)
When the lamp is connected, the current value for the initial starting current will rise.
It is less than the current value during the dull period, and spatter occurs when electricity is applied.
Set to a current value that can be started without
It is characterized by having a timer (20) for.

According to this, by setting the predetermined period immediately after the lamp is started by the timer (20) and changing the setting of the voltage limiter circuit (17) only during that period, the current value in the predetermined period immediately after the lamp is started is changed. The size can be reduced and the lighting method according to claim 1 can be implemented.

A lighting device for a high pressure discharge lamp according to a fourth aspect is the lighting device according to the third aspect, wherein the voltage limiter circuit (1
7) is equipped with a shunt regulator (27)
The setting of the voltage limiter circuit can be changed by changing the voltage value input to the reference of the shunt regulator (27) using the signal of (20).

According to this, the reference input of the shunt regulator (27) of the voltage limiter circuit (17) can be changed by the timer after a predetermined time. As a result, it is possible to easily reduce the current value for a predetermined period immediately after starting the lamp and increase the current value after the lapse of the predetermined period.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to preferred embodiments.

[Embodiment] Similar to the above-mentioned conventional example, as an example, 270 W, bulb outer diameter 14.5 mm, arc length 1.3 mm, cathode 1.4 mm diameter tungsten mandrel, internal pressure at lighting is about 150.
An ultra-high pressure mercury discharge lamp of atmospheric pressure was prototyped, and lighting was attempted and verified by the lighting method of the present invention.

The reason why the blackening phenomenon is remarkable and the luminous flux maintenance factor is remarkably lowered when the lamp is repeatedly turned on and off in the above-mentioned conventional example is due to the cathode structure having only the mandrel.

As shown in FIG. 8, the arc spot (51) at the time of starting is initially located at a place far from the tip of the electrode (50),
While moving on the surface of the electrode, it gradually moves to one point of the tip of the electrode and becomes a stable arc spot (52).

Sputtering due to impact is prominent during the period when the arc spot is unstable at the initial stage of starting. Therefore, I tried to reduce the constant current value at the initial stage of startup to 5A.

When the constant current value was lowered to 5 A, the current sputtering at the time of starting could be greatly reduced, and no blackening was found even after turning on and off about 50 times, confirming that there was no problem.

However, the rising time in this case becomes as long as about 120 seconds as shown in the "curve B" of FIG. 5 for explaining the lamp rising, and it may not reach the stable lighting region depending on variations and air cooling conditions for the lamp. there is a possibility.

Therefore, in the present invention, the current is lowered only during the period in which the arc spot at the initial stage of lamp startup moves on the surface of the cathode mandrel, for example, the current value is set so that the starting performance is not impaired. In this example, the experiment was conducted for 3 seconds at 4A.

Since the period during which the arc spot moves on the surface of the cathode mandrel is within 10 seconds, it is preferable that the period during which the low current is supplied at the initial stage of startup is within 10 seconds.

Further, the current value at the initial stage of starting is preferably 0.5 to 0.9 times the current value of the substantially constant rising current. This is 0.
This is because if it is less than 5 times, the startability is adversely affected, and if it exceeds 0.9 times, the influence of spatter due to the impact at the beginning of starting becomes large.

Then, the arc spot moved to the tip of the cathode and was made to stand still, and then the current was increased. The current value at this time was 7 A in this embodiment. “Curve A” in FIG. 5 shows how the lamp rises at this time, and the light amount is 5
It took about 60 seconds to reach 0%.

By such a lighting method in which the initial current value at the time of starting the lamp is kept low, the occurrence of spatter is extremely small even in the cathode tungsten electrode having only a mandrel without a coil,
In addition, a lighting system with a good start-up could be realized.

It has been found that the constant current value during the lamp rising period is properly in the range of 1 to 2 times the current value at which constant power can be supplied at the specified minimum voltage during stable lighting of the lamp. If it exceeds 2 times, the load on the electrode becomes remarkable and it becomes a cause of shortening the life.

FIG. 1 is a diagram for explaining the power control characteristics according to the lighting method of the present invention, showing the lamp current characteristics and the lamp power characteristics with respect to the lamp voltage. Also, FIG. 3 shows a waveform for explaining the lamp current at the time of starting according to the lighting method of the present invention.

Next, the lighting device according to the present invention will be described.

FIG. 6 is a diagram showing an embodiment of a lighting device according to the lighting method of the present invention.

The DC power supply (1) supplies an output open circuit voltage (OCV) which is particularly necessary for starting the lamp (5), and is usually 200 V or higher.

The output of the DC power supply (1) is the down converter (2)
Is supplied to. The down converter (2) is a switching element (11), power diode (12), choke coil (13).
And a smoothing capacitor (14) to form a step-down chopper of a typical switching power supply.

The output of the down converter (2) is connected to a voltage detection circuit (7) for detecting the output voltage and a current detection circuit (6) for detecting the output current. The detected voltage and current are input to the arithmetic circuit (8) and fed back to the switching element (11) of the down converter (2) via the pulse width modulation circuit (9).

The down converter (2) has a high frequency (tens of kHz to
Switching is performed at several hundred kHz, and in order to supply constant power after stable lighting of the lamp, the detected output voltage and output current are calculated and the pulse width is controlled by the pulse width modulation circuit (9). Is working. The voltage detection circuit (7) simply divides the voltage by the resistor (28) and the resistor (29) and outputs it.

For the current detection circuit (6), a low resistance of, for example, 1Ω or less is generally used. Choke Coil (13)
A smoothing capacitor between the output terminal (positive side) and the reference potential
(14) is connected. This is to reduce the effect of ripples that occur due to the down converter (2) switching at a high frequency (tens of kHz to hundreds of kHz). Typically, the ripple content is 5% or less, and 0.1 μF to 10 μF is generally used.

The arithmetic circuit (8) includes a voltage detection circuit (7) for detecting an output voltage, a buffer circuit including an operational amplifier (19), an operational amplifier (18), a reference voltage (22), resistors (32) and (33). Input to the adder circuit (15) via the inverting amplifier (18) composed of the above, and the signal of the current detection circuit (6) that detects the output current is input to the adder circuit (15) so that the lamp is stable during stable lighting. Power characteristics can be achieved.

The substantially constant current characteristic during the ramp rising period can be achieved by adding a voltage limiter circuit (17) to the output of the inverting amplifier (16).

In the voltage limiter circuit (17), the shunt regulator (27) is generally used, and the voltage divided by the resistors (30) and (31) is input to the reference of the shunt regulator, and the voltage is below the required lamp voltage. Can be set to a substantially constant current.

As a result, for example, the constant current value of 7 A at the time of rising in FIG. 1 is determined.

In order to set the current value during the period when the current value at the time of lamp starting is small (soft start) to a required value,
It can be achieved by connecting the output of the timer (20) that can set a predetermined period immediately after start-up to the reference of the shunt regulator (27) through a series circuit of a diode (39) and an appropriately set resistor (40). .

That is, by using the timer (20), the voltage value input to the reference of the shunt regulator (27) is changed only for a predetermined period immediately after starting, and the current value is made a small value suitable for soft start.

The state of the output voltage of the inverting amplifier is shown in FIG.
Here, the states of the limiter at the time of rising and the limiter at the time of soft starting are shown, and thereby the output current control characteristic shown in FIG. 1 is created.

[0062]

As described above, according to the method of the present invention,
In particular the arc length short 2mm to 400W or less of the high-pressure discharge lamp in the following with the dc lighting, in the case of using the tungsten electrode of the electrode melting hard single mandrel as a cathode, before
The current value of the approximately constant current during the ramp rising period is
Constant power can be supplied at the specified minimum voltage during stable lighting
The current value is equal to or less than the current value, and the starting initial current
Is less than or equal to the current value during the ramp rise period.
Therefore, spatter does not occur when energized and the start range is
The current value is set, and in the device of the present invention,
When the current value during the lamp rising period is stable
Below the current value that can supply constant power at the specified minimum voltage of
Voltage limiter circuit that regulates the
It will be connected to the voltage limiter circuit in the following predetermined period.
The current value of the initial starting current is
The current value is less than the current value, spatter does not occur during energization, and
To set the current value within the range that can be started.
Since the timer is provided, the current can be appropriately set to a low value for a few seconds immediately after the start to prevent the electrode from spattering, and the load on the electrode can be reduced. As a result, the original long life of the lamp can be maintained.

Moreover, since the arc spot moves to the tip of the electrode and after standing still, the current can be set appropriately high to accelerate the rise time of the lamp, so that the startability is not impaired.

The present invention is particularly effective for an ultra-high pressure mercury lamp in which the load on the electrodes delicately affects the life of the lamp.

[Brief description of drawings]

FIG. 1 is a diagram illustrating power control characteristics according to a lighting method of the present invention.

FIG. 2 is a diagram illustrating power control characteristics according to a conventional lighting method.

FIG. 3 is a waveform illustrating a lamp current at the time of starting according to the lighting method of the present invention.

FIG. 4 is a diagram showing waveforms for explaining a lamp current at the time of starting by a conventional lighting method.

FIG. 5 is a diagram for explaining ramp-up.

FIG. 6 is a diagram illustrating an example of a lighting device according to a lighting method of the present invention.

FIG. 7 is a diagram illustrating a limiter characteristic of power control according to the lighting method of the present invention.

FIG. 8 is a diagram illustrating an arc spot at the time of starting.

[Explanation of symbols]

(1) DC power supply (2) Down converter (4) Igniter (5) Discharge lamp (6) Current detection circuit (7) Voltage detection circuit (8) Arithmetic circuit (9) Pulse width modulation circuit (11) Switching element (12) ) Power diode (13) Choke coil (14) Smoothing capacitor (15) Adder circuit (16) Inverting amplifier (17) Voltage limiter circuit (18), (19) Operational amplifier (20) Timer (22) Reference voltage (27) Shunt regulator (28), (29), (30), (31), (32), (33), (34), (40) Resistance (39) Diode (50) Electrode (cathode) (51) Immediately after starting Unstable arc spot (52) Stable arc spot several seconds after starting

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Claims (4)

(57) [Claims] 1. A rare gas and mercury are enclosed in an arc tube,
This is a method of lighting a high-pressure discharge lamp with an arc length of 2 mm or less and 400 W or less, and a tungsten electrode of the cathode composed of a single mandrel, using a DC lamp current. Supply, then controlled at a substantially constant current during the lamp rising period, then at a constant power during lamp stable lighting, the current value of the substantially constant current during the lamp rising period during stable lamp lighting Above the current value capable of supplying a constant power at the specified minimum voltage, the current value of the starting initial current is below the current value during the lamp rising period , spatter does not occur during energization, and
A method of lighting a high-pressure discharge lamp, characterized in that the current value is within a range in which it can be started . 2. The method for lighting a high pressure discharge lamp according to claim 1, wherein the fixed period of time at the beginning of the lamp is 10 seconds or less. 3. A direct current for lighting a high pressure discharge lamp is supplied.
A DC power source that includes a current detection circuit for detecting a lamp current as a detection voltage, and a voltage detection circuit for detecting a lamp voltage as a detection voltage, is connected to the direct current power supply, the lamp current detection voltage and the run
A down converter for controlling the power of the high-voltage discharge lamp based on the detected voltage detected by the voltage detector, an inverting amplifier that inverts and amplifies the detected voltage detected by the voltage detection circuit, a detected voltage detected by the current detection circuit, and the inverted circuit. an adder circuit for adding the output of the amplifier, and to perform the pulse width control to the down converter based on the output of said adder circuit performing the power control of the high-pressure discharge lamp
A pulse width modulation circuit for, connected to the output of the inverting amplifier, rising the lamp
The current value during the charging period is the specified minimum voltage during stable lighting of the lamp.
Prescribed to be below the current value that can supply constant power
And a voltage limiter circuit for a predetermined period immediately after starting the lamp.
It is connected to the circuit and the current value of the initial starting current is
It is less than the current value during the rising period and spatters when energized.
Is set so that the current value does not occur and is within the startable range.
A lighting device for a high-pressure discharge lamp, which is provided with a timer for setting . 4. The voltage limiter circuit can change the setting of the voltage limiter circuit by changing a voltage value input to the reference of the shunt regulator utilizing and timer signal comprises a shunt regulator
Lighting apparatus of the high-pressure discharge lamp according to claim 3, characterized in that the so that.